I'm not familiar with most of the Mitsubishi engines. I know they made side valve, air cooled stationary engines something like Briggs ones, from 1946 and built them into a scooter, and probably other products as well. They were 1.5 hp initially. By 1960 they had 175 and 200 cc versions (I had one of the 1960 200 cc scooters). So, if it is Mitsubishi it might even be older than 30 years, and perhaps a collector's piece. The engine in my scooter was a decent unit.
If it actually is Mitsubishi, it should have identification cast into the crankcase I think: at least their 3 diamonds emblem.
